1. Field of the Invention
The present invention relates to an exposure method which utilizes exposure patterns that have undergone an optical proximity correction (OPC), an apparatus for generating optical proximity corrected exposure data, and an exposure apparatus for the optical proximity corrected exposure data.
2. Description of the Related Arts
An optical proximity effect is known in which, in LSI exposure step, according to a frontward dispersion and rearward dispersion of exposure beams, a pattern is expanded in a region where a pattern density is high and a pattern is thinned in a region where the pattern density is low. According to such the optical proximity effect, when a pattern is exposed on a reticle mask and developed in accordance with the exposure data generated from design data, and further the pattern is exposed on a chip and developed by utilizing the reticle mask, the pattern of the reticle and the pattern of a wafer lead to a profile different from the original exposure pattern.
FIG. 1 is a diagram showing one example of the optical proximity effect. FIG. 1 shows how two kinds of pattern 1, 2 change by the optical proximity effect in the exposure pattern (1), the pattern on the reticle (2), and the pattern on the wafer (3). The square pattern 1 is a rectangular profile whose four corners are made at 90° in the exposure pattern, but when the reticle is exposed with laser beams, electron beams, or the like by utilizing the exposure pattern and developed, the pattern on the reticle leads to a profile whose four corners are slightly rounded like a pattern 1A. Furthermore, when the wafer is exposed by utilizing the reticle pattern and developed, the pattern to be formed on the wafer leads to a profile whose four corners are rounded like a pattern 1B, as shown in FIG. 1, and the square becomes approximately a round shape. This occurs by a cause that the frontward dispersion and rearward dispersion from peripheries are scarcely affected at the corners, and this cause is equal to a cause that leads to a phenomenon that a top end of a line pattern becomes a round profile, and further is thinned.
Furthermore, in the case where other patterns 3, 4 are present in proximity to the linear pattern 2, a slightly expanded profile is obtained in positions confronting the patterns 3, 4 on the reticle, as shown in a pattern 2A. This occurs by a cause that the frontward dispersion and rearward dispersion are generated due to exposure energy to the patterns 3, 4, and influences from a more proximal pattern 4 are greater. And, further when the wafer is exposed and developed by exploiting the reticle pattern, a largely expanded profile is obtained in positions confronting the patterns 3, 4, as shown in a pattern 2B.
FIG. 2 is a diagram for explaining the optical proximity correction (OPC). Taking into consideration the optical proximity effect of FIG. 1, a serif pattern 1C is added to the four corners of the square exposure pattern 1, and the reticle pattern 1A and the pattern 1B on the wafer are formed by exposing and developing according to the OPC corrected exposure pattern. The reticle pattern 1A is deformed to a profile that the corners are rounded by the optical proximity effect, and the corner of the wafer pattern 1B becomes a sharp right-angled profile. Furthermore, in the linear exposure pattern 2, a recess part 2C is added to the positions confronting the patterns 3, 4, and the exposure and development are made by the OPC corrected exposure pattern. As a result, a slightly recessed profile 2D is obtained in the reticle pattern 2A and a flat line profile is obtained in the wafer pattern 2B.
The above-described OPC is similarly effective even in the case where the exposure and development are made by drawing directly on the wafer with the electronic beams according to the exposure pattern data.
As set forth above, it is possible to restrict a profile change of the patterns after being exposed and developed accompanied by the optical proximity effect by making the OPC in the exposure pattern, and to increase the pattern precision. However, in the OPC corrected exposure pattern, a simple square or rectangle is not formed in the aforementioned example, thereby causing an increase in the number of exposure patterns. Such the increase in the number of exposure patterns leads to an increase in an exposure data amount, and an increase in a transfer time of the exposure data to an exposure apparatus, and an increase in a rendering time for bitmapping in the exposure apparatus, and a reduction in a throughput in an exposure step.